The invention relates to displaceable X-ray examination table. The table top is displaceable by an endless chain which cooperates with a drivable sprocket.
A device of this kind is described in U.S. Pat. No. 3,473,024. The sprocket is driven by a motor, if necessary. When the motor of such an apparatus is stopped, the drivable sprocket is blocked in order to lock the table top in its position.
The chain of such a device is loaded by the forces acting on the table top. A broken chain could therefore endanger a patient resting on the table. In order to avoid the danger imposed by such a break, there are government regulations which effectively require a twelve-fold static protection if no additional protection is provided to prevent the table top from falling if the chain breaks. This means that the chain must be designed to bear twelve times the static load exerted by the table top during normal operation.
However, if such protection against falling is provided, the situation will be less critical if the chain breaks. In that case, the chain must be designed to bear merely for four times the highest load.